Problem: Define $A\star B$ as $A\star B = \frac{(A+B)}{3}$. What is the value of $(2\star 10) \star 5$?
Answer: We have $2 \star 10 = \frac{2+10}{3} = \frac{12}{3} = 4$. Then $4 \star 5 = \frac{4+5}{3} = \frac{9}{3} = \boxed{3}$.